Process for the separation or recovery of gases and vapors by solid adsorbents



Jan.l 7,1930. A, GODEL PROCESS FOR THE SEPARATION OR RECOVERY OF GASES AND VAPORS BY SOLID ADSORBENTS Filed June 23. 1926 2 Sheets-Sheet.

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A. GODEL PROCESS FOR THE SEPARATION OR RECOVERY OF GASES AND VAPORS BY SOLID ADSORBENTS Filed June `25. 1926 2 Sheets-Sheet Jan. 7, 1930.

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Patented Jam 7, 1930 unirsi' STATES Minima eoDEL, or' anonimi, FRANCE, assreuon 'ro soorrit DE anonnacnns nrv nnxrrorrn'rrons rnrnonrrnnns, or. raars, rnauor., a rennen soornri. an"

NYME Y' .PROCESS FOR THE SEPARATION '0R RECOVERY 0E' GASES AND VAPORS FY SOLID ADSOENTS Application led June 23, 1926, Serial No. l1@,006, and in Great Britain May 28, i926?.

`. In the known processes usually employed for the `se} )arat-ion or recovery of gases and vapors by solid adsorbents, such as activated carbon, silica gel, and the like, advantage is 5 taken of the selective adsorbent power olfa the said solids in order to extractV and retain certain gases or vapors mixed with other gases,

the adsorption having to take place in definite conditions of pressure and temperature.

V purpose arranged in any suitable vessel, stationary orV movable, traversed by the gas to be treated; the adsorbent can be introduced intoand extracted romtthe vessel in a continuous manner or it may be introduced and left there.

in without extraction, the said vessel lbeing filirrentlydesignated adsorber or adsorption ter. l.

If the nature of the adsorbent and the con- 10 ditions of pressure and temperature have been suitably selected for an eiiicient adsorption of the product to be recovered, there will be a progressive saturation of this substance in proportionas the gas circulates in the ad- 'f sorber. The passage of the gas can be arrested, by isolating the adsorber from the circuit, when the saturation of the adsorbent is considered suiiicient.

Itis then merely a question ofse'parating 3f) or recovering from the adsorbent the product adsorbed thereby, this operation likewise rendering the adsorbent iit for a further adsorption; this operation is currently designated the recuperation, reactivation or re- 3" generation stage in opposition to the period of adsorption which has preceded it. The recuperation is eifected by v an injection or' steam or water vapor, generally superheated, into the adsorbent mass.

Having regard to the known development 'of these operations, the present invention has ior its main object to eiect a large economy of steam in the operation of recuperation or regeneration of the adsorbent. i5 lin the processes known hitherto, the expen- The solid serving as adsorbent is for this diture, of steam has been considerable. it can be reduced by one half or more by a better utilization of the available heat units, according to the improved process hereafter described.

Fora more complete comprehension of the advantages of the invention, there are represented diagrammatically1 and by way or" examples on the accompanying drawings:

Figure 1, an installation currently elnployed for the recuperation of voiatile solvents or hydrocarbons by solid adsorbents, for example, by activated carbon.

Figure 2, an installation having the same object, arranged in accordance with the present invention, with direct superheating of the Steam derived from a irst adsorber before its passage into a second adsorber.

Figure 3, a modified installation, also arranged in accordance with the present invention.

ln the usual process, as indicated in Figure l, the steam produced by the boiler C is led by any suitable pipe system to the superheater S, and then passes to the lter F, filled with adsorbent material, in which the gas to be treated has previously circulated during the adsorption period. This gas enters the filter'by the pipe t, traverses the adsorbent material, and then escapes by the pipe latter having given up the products to be recovered (benzol, Gasoline, etc.). The said pipes t t1 are close as soon as the adsorbent mass is sufficiently saturated.

Dry steam is then admitted into the iilter F and in circulating therein this steam displaces the adsorbed products from the adsorbent material, carrying them over to the refrigerator R. The condensation water, as well as th'e products carried over and con# densed which are not miscible with water, will separate out by density in the fiorentine or settling tank A; the product recovered is collected at the outlet a while the water escapes from the lower level at the point al. In case the product recovered is miscible or partly miscible with water, it may perhaps be neces. sary to effect a distillation of the condensate,

because separation by density will not be suffcient.

Numerous improvements in this process are known having for their object to effect a eertain economy of steam; in particular it has been found advantageous, before proceeding to inject steam into the adsorber, to heat the adsorbent mass to a temperature exceeding '100 C. by suitable means such as internal heating coils. This method avoids the condensation of too large a quantity of steam in the adsorbent mass, which would have the disadvantage of necessitating considerable expenditure of dry steam for its subsequent evaporation.

It is nevertheless impossible by that improved method as by all those hitherto rought into operation, to prevent the condensation of a large quantity of water'. in the adsorbent mass.

Further, according to the degree of superheatof the steam employed, in order to evaporate the water condensed in the adsorbent, there will be required a varying quantity of steam, possibly amounting to ten times more than the water to be evaporated from thev separately, but also of recovering the latent condensation heat of this steam, this heat recovery or recuperation being effected with a view to the economical and simultaneous treatment of a fresh adsorbent mass.

Now, the latent heat of steam is much greater than the superheat alone, as actually ein-- ployed in the prior processes. It results therefore on balance that there is a considerable saving of steam due to the fact that the condensation heat units are recuperated by the method of the present invention.

One method of carrying out the invention consists in providing two adsorption filters F F1 (see Figur( 2), mounted in series as regards their steam connections. In the first first lace, the gaseous mixture to be treated is le into these filters by pipes t t respectivel these being connected to the main pipe T;

e mixture circulates therein until the adsorbent mass is sufiiciently saturated with the product to be recovered, and then after having yielded up the product the gas leaves by the pipe@4 tf1 t1', which are likewise connected to a main pipe T1. As soon as the adsorbent mass is saturated, the pipes t t1 and t t1 are the adsorption filters F F1, the steam derived from the boiler C and superheated at S is passed into the filter F. At the start of the operation, the steam condenses, heating the filter F and the adsorbent mass. The steam then displaces the` product to be recovered from the adsorbent mass and at the same time progressively dries this adsorbent mass to the extent of the available superheat. i

The steam leaving the filter F is therefore charged with the product recovered; it is in the/state of saturated or wet steam, having given up its superheat. A part of the Water may even escape in the condensed state and it will therefore be well to provide a steam trap or drain cock at the exit from the first adsorber.

According to the invention, the steam leaving the filter F is utilized directly, after a secondl superheat applied by a superheater S1, for the regeneration of a second filter F1.

densation heatv of the steam is utilized, ob- Viatingthe use of an equal quantity of steam for t-he treatment of the said filter F1.

The steam, again enriched with the product to be recovered, is condensed together` with thisproduct in a refrigerator R, the separation of the liquids being effected by a florentine or settling tank A or by any other means.

4In this way the whole of the latent or con- Afterthe passage of a suflicient quantity of superb-cated steam through the filters F and F1, the adsorbent material will have been restored or reactivated, dried and freed from any adsorbed product; it is therefore ready for a fresh adsorption operation. This adsorption may be carried out directly or after lie-cooling of the adsorbent mass, the whole being effected by Well known means.

It is evident that the back pressures or losses of head in thetwo filters F F1 and in the superheater S1, are cumulative, leading to a certain excess of pressure in the filter F, but experiment has shown that no inconven ience results therefrom.

The same however does not apply in certain cases for theV use of a superheater interposed between the two filters F F1, which may present the disadvantage of producing the cracking of certain recovered products carried over with the steam; a method ot obviating such cracking is explained hereafter. h

In order to avoid the above-mentioned maaar? cracking, the operation may be carried out under vacuum, which reduces the temperature of superheat necessary for the treatment of the filters. The operation may likewise be carried out accordingto a dillerent general arrangement, represented in Figure 3.

In this modified arrangement, an evaporator E is interposed between the ilter F and the superheater S1; the remainder ofthe installation is arranged as in the previous case.

The steam leaving the vrst lilter, loeing charged with the product to be recovered so that' it cannot be employed directly after superheating is utilized to produce the evaporation' of a. substantially equal quantity- Ot pure Water, the exchange being etl'ected in an evaporator el' any suitable type; in most cases this will be a decreasing-pressure evaporator, but there may be used for example an evaporator with steam-compression or anl evaporator operating by release ot liquid.

Figure 3 applies especially to the case in i which there is utilized an evaporator of the decreasing-pressure type.

At leaving the iirst lil-ter F the steam charged 1with the product to be recovered passes to the evaporator E in which it condenses wholly or in part, or again equally A v"with the product to oe recovered. rl`he Water ration tank.

ot condensation may he discharged from the hase of the evaporator and evacuated directly or again it may he passed together with the uncondensed vapors into a refrigerator R as represented in Figure 3. The pure water vapor or steam generated bythe evaporator E is directed intothe superheater S1 before passing into the second filter F1 in communication with another refrigerator ltl and a fiorentine or settling tank Alf y The refrigerator lt is likewise followed hy a fiorentine tank A for the decantation ot the distillate.

The vsupply of water to the evaporator may 1 in certain cases be effected with advantage hy means of decanted hot Water drawn oilu trom the high pressure compartment oit' the evapo- According to the arrangement shown in the decreasing-pressure type, as for an evaporator operating by release of liquid, there will necessarily exist a considerable fall of steam pressure, resulting in certain cases in a fairly high-pressure in the first a'dsorber, this pressure amounting for example to as much as one or even two kilogrammes per square cent1- metre (gaugepressure). This back pressure does not present any disadvantage as regards `satisfactory* operation, 4as will he explained further on.

In certain cases, if it were found desirable, the two ,adsorhers F El of Figures 2 or'3 might be grouped in a single metal casing, the general idea of the invention remaining unaected. n

lf a steam-compression evaporator were employed, the secondary steam derived from the evaporator might without going beyond the scope of the invention be introduced into the circuit ot the primary steam serving for the treatment of the rst iilter F; in that case the lter F1 might be suppressedn y, v

For this purpose -the steam generated in the evaporator would have to be compressed to a pressure allowing' it to re-enter the circuit ot' the primary steam in advance ot the iirst superheater.

This compression might with advantage be produced by an injector of the Koerting type, utilizing the primary steam on its Way to the superheater b; this injection steam would then have to be generated by the boiler C at a suH-icient pressure for example 7 to 8 hilogrammesper square centimetro.

Lastly the use of an evaporator operating by release of liquid is particularly suitable if condensation water trom the high pressure compartment of the evaporation tank can be used tor the circulation with release; this will he possible when the product to loe recovered is not misoihle with Water and can be separated readily 'therefrom hy decantation in the evaporator itself. Moreover the rate of working and the temperature of the evaporator can be regulated so that there shall none of these arran ements allows ot recovering any considera le quantity of the heat units lost in the condensation nor do they in any case allow simultaneous treatment with steam ol two adsorhers or the like. Y

ln particular the -vvell lrnown principles of multiple-eHect evaporation have never been applied advantageously tor the regener- Figure 3, and by the use ot an evaporator ot ation of solid adsorhents. New, it has been shown that such regeneration is possible and that the main disadvantage resulting from the excess or back pressure to he maintained in the lirst iilter can easily he surmounted for the following reasons z-An eective pressure, of some atmospheres for example7 does not prevent at all or to' any appreciable extent the evolution of the volatile products contained in the adsorbent when' it is treated with superheated steam at this pressure. rIhe adsorbent can be perfectly regenerated and dried by superheated steam under pressure, on condition of regulating the, temperature of the superheat as a function of the pressure in question; in practiceit will he suflicient to utilize in all cases steam possesslll@ 'loll lll@ ian l ,fected by saturated steam.

According to the invention it is possible to provide likewise more than one stage of recuperation of the steam utilized and thus Ato regenerate simultaneously more than two tilters containing adsorbent substances. It will suice for this purpose to arrange in sequence 'several apparatus such as described with regard to Figures 2 or 3. In this respect the only limitations will be as regards the complication of the apparatus and the excessive counter pressure caused in the earlier adsorbers.

To a certain extent the second drawback can be remedied by arranging after the refrigerator o the last adsorber, a suction pump or any other apparatus adapted to fulfill the same function.. Treatment under vacuum may likewise be advantageous in the case in-which only two adsorbers 'are employed.

For example in the installation represented in Figure 2, the two filters F and Fl may be Worked under vacuum' simultaneously by, the addition of a suction pump after the refrigerator R. This arrangement will'have the advantages of allowing satisfactory oper-v ation at a fairly low temperature of superheated steam, and of allowing for example the replacement of ordinary superheaters heated by.direct flame by simple tubular ex-v changers heated by high pressure steam.

For the arrangement of Figure 3, the vacuum apparatus may be placed at the exit from the second refrigerator R1, which would allow of eecting the evaporation under vac- .uum in the evaporator E; the calorilic ei-4 ciency of theV evaporator would be considerably increased thereby. Moreover, the coun ter preure in advance of `the evaporator,

'or even suppressed completely.

that is to say inthe filter F, would be reduced In all `cases the vacuum pump may beduplicated by means for the extractionof condensation liquid.

The present invention can be applied simultaneously in combination with any other accessory arrangement tending likewise to roduce an economy of steam consumption.

What I claim is 1. In a process f o'r the recovery of volatile products by solid adsorbents with regeneration b steam, the improvement consisting in utilizing the steam leaing` an adsorber for heating an evaporator, and superheating the secondary steam produced in said evaporator in order to `serve for the regeneration of an adsorbent mass.

2. In a process for the recovery of volatile products by solid adsorbents with regeneration by steam, the improvement consisting in using an evaporator for condensing the steam leaving an adsorber, and superheating the secondary steam produced in said evaporator in order to serve for the regeneration of an adsorbent mass. y

3. In a process for the recovery of volatile products by solid adsorbents with regcnration by steam, the improvement consisting in using an evaporator for condensing the steam leaving an adsorber, and compressing the secondary steam produced in said evaporator in order to allow of its re-introduction into the primary steam circuit at an earlier point.

4. In a proccssfor the recovery of volatile products by solid adsorbents with regeneration by steam, the improvement consisting in recuperat-ing the latent heatof the steam leaving an adsorber, and utilizing said latent heat in the regeneration of another adsorber, said adsorbers being connected in series during the regeneration. y

5. In a process for the recovery of volatile products by solid adsorbents with regeneration by steam, the improvement consisting in recuperating the latent heat of the steam leaving an adsorber,l utilizing said latent heat in the regeneratien of another adsorber,' and applying suction' to the latter adsorber.

6. In a process for the recovery of volatile products by solid adsorbents with regeneration by steam, the improvement consisting in recuperating the latent heat of the steam leaving an adsorber, utilizing said latent heat in the regeneration of another adsorber Working ata lower pressure than said adJ sorber first mentioned, and adding the balance of heat necessary for the regeneration of the latter adsorber, without cracking the recovered products by such'added heat.

7. In a process for the recovery of volatile products by solid adsorbents with regeneration by steam, theimprovements consisting in providing a plurality of vadsorbers into which the matter for treatment can, be circulated, said adsorbers Working at successively decreasing pressures, passing superheated steam through said adsorbers in series at the conclusion of an adsorption operation, re-

Asuperheating the-steam leaving one adsorber' before it enters the next,condensing the steam leaving the last adsorber, and separating the recovered products from the condensate.

8. In a process for the recovery of volatile products by solid adsorbents with regeneration by steam, themprovements consisting in providing a plurality of adsorbers into which the matter for treatment can be circulated said adsorbers working at successively decreasing pressures, passing superheated .steam through said adsorbers at the conclusion of an adsorption operation, utilizing the latent heat of the steam leaving one adsorber and adding superheat thereto for the regeneration of the next adsorber, condensing the steam leaving the last adsorber, and separating the recovered products from the condensate. lo In testimony whereof I hereunto aix my signature.

ALBERT GODEL. 

